Aubrey Plaza was telling her friends about a Hilary Duff concert she'd just been to when she looked at her right arm and realized she was unable to move it. She felt confused and suddenly blacked out. When she regained consciousness, she couldn't speak; only bizarre sounds would come from her mouth.

"My friends thought I was [messing] with them, that it was some weird joke," she recalled, using cruder language. "That's what I get for [messing] with people so much."

At 20, Plaza was having a stroke. But because part of her shtick is to toy with others — her comic delivery often so dry and unemotional that it's hard to tell when she's being serious — even her rare medical emergency was nearly overlooked. Plaza made a full recovery, but even now, at 29, she's not sure what caused the stroke.

"I remember thinking it was possible that I'd never talk again — that I would never act again. I had really dark moments like that when it happened," she said. "It probably has informed my attitude toward life as an adult. I feel like I maybe appreciate things a little more than I would have."

It was a rare vulnerable moment for Plaza, who is resistant to letting anyone see past her deadpan veneer. After all, dry humor has become her trademark ever since she began playing the lackadaisical April Ludgate on "Parks and Recreation" four years ago. But now many audiences will see Plaza play something other than sarcastic in the R-rated comedy "The To Do List," set to open July 26. The comedy, a coming-of-age story peppered with frank sexual discussions, is aimed at the same female audience that made "Bridesmaids" a hit.

Plaza is one of the few comic actresses building a career in film and TV who doesn't come from a stand-up background. Though best known for her role on the NBC sitcom, she has slowly been bulking up her big-screen résumé since her memorable cameo as Seth Rogen's character's girlfriend in 2009's "Funny People." Last year, she earned strong reviews for her portrayal of an intern who falls for a wannabe time traveler in the indie Sundance favorite "Safety Not Guaranteed."

"The To Do List," written by first-time feature director Maggie Carey, is a departure for Plaza. As Brandy Klark, a high school valedictorian hellbent on losing her virginity before she heads off to college, she's far more zealous than droll. She's in nearly every frame of the movie, her most commercial release.

"It wasn't like I had the control of being able to say, 'And this will be my first lead role,'" she said. "If Maggie hadn't been directing it, I don't know if I would have been offered the part. I feel like I often think, 'God, I'd really like to play that character but they wouldn't think of me' — or if they did, I would be a risk to take."

Is she serious?

Plaza sat at a vinyl booth at the 101 Coffee Shop, a diner housed in a Best Western where she stayed for a few weeks when she first moved to L.A. She lives a couple of miles away now, in a Los Feliz home she shares with her boyfriend, screenwriter Jeff Baena, who wrote "I Heart Huckabees."

"Do you hate it here?" she asked, looking over a menu. She ordered two eggs sunny side up with veggie sausage — no toast — but when the dish arrived at the table, she looked displeased.

"Ew, this looks weird," she said, stabbing her fork through the faux meat and bringing it closer to her face to examine before taking a bite. "This is the grossest thing I've ever eaten. No! It tastes really good."

It was hard to tell whether she was being serious, as it so often is — a power over others she seems to relish. On late-night talk shows, she frequently acts uninterested, rarely raising her voice above a monotone and refusing to answer questions earnestly.

"I would like to see the person who can throw her off her game," quipped filmmaker Carey, who met Plaza when the two were students at the Upright Citizen's Brigade Theatre, which puts on improv and sketch comedy shows.

It's an act you either find oddly hilarious or annoying. In April, for instance, during the MTV Movie Awards, Plaza ran onstage with "The To Do List" written across her chest in felt pen while Will Ferrell was accepting a prize. Without saying anything, she half-heartedly tried to steal the actor's golden popcorn prize and was then kicked out of the telecast. At best, viewers were left confused; at worst, irritated.

"I don't know why I do it. I can't help it! I don't ever [mess] with people in a mean-spirited way," she insisted. "I'm really nice. I'm nice! I just sometimes don't know what else to do."

Growing up in Wilmington, Del., Plaza said, she wasn't known as a "deadpan, sarcastic person."

"I was known as 'the Whore,'" she said, breaking into a smile.

In fact, she was actually rather chaste, attending a strict, all-girls Catholic school where the "religious implications" of sex before marriage were frequently emphasized.